Project Summary/Abstract Accumulated DNA damage is recognized as a causal factor in the initiation and progression of atherosclerosis. Genomic instability in the vascular smooth muscle cells (SMC) leads to cell apoptosis and contributes to atherosclerotic plaque vulnerability. Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) is the major cellular sensor ultimately responsible for maintaining of cellular homeostasis, however its specific role in atherogenesis is completely unknown. It has been shown that a key pro-atherogenic lipid OxLDL downregulated GAPDH in human aortic SMC and that GAPDH expression was markedly decreased in the atherosclerotic plaque SMC and that low GAPDH level was associated with increased apoptosis. GAPDH reduced DNA damage and suppressed SMC apoptosis via a novel molecular mechanism involving nuclear GAPDH interaction with apurinic/apyrimidinic endonuclease 1 (Ape1), the major oxidized DNA repair enzyme. SMC-specific GAPDH overexpression decreased DNA damage, reduced plaque SMC apoptosis and decreased atherosclerotic burden. Importantly, atherosclerotic plaques in GAPDH-overexpressing mice had elevated SMC levels, increased collagen, reduced necrotic cores and thicker SMC-rich fibrous caps suggesting enhanced plaque stability. The major focus of the current proposal is to study the mechanism mediating GAPDH-induced anti-atherosclerotic and plaque stabilizing effect and to determine whether GAPDH mimicking peptide (GMP) reduces atherosclerotic burden and improve plaque stability in atherosclerotic mice. The main hypothesis is that GAPDH reduces atherosclerotic burden and enhances features of plaque stability via stimulation of Ape1-dependent DNA repair and suppression of SMC apoptosis. This will test the hypothesis in following Specific Aims: Specific Aim 1: To demonstrate that SMC-specific GAPDH regulates DNA repair, apoptosis, atherosclerotic burden and features of plaque stability and identify mechanism. Specific Aim 2: To determine whether GAPDH-mimicking peptide (GMP) will activate Ape1, stimulate DNA repair, suppress cell apoptosis and reduce atherosclerosis. Proposal will use adeno-associated viruses (AAVs) to perform SMC-targeted GMP cDNA transfer in atherosclerotic mice. AAV-based vectors are approved to use in humans, therefore the long-term goal is to use the AAV-GMP vector as an innovative pro-DNA repair and anti-apoptotic therapy to treat unstable atherosclerosis. Studying of anti-atherosclerotic effects of GAPDH and demonstration that GMP induces plaque-stabilizing effect will lead to the development of novel targeted therapies to treat atherosclerosis and prevent acute vascular events.